IMR 4064 was the most accurate powder for the 8mm JS Mauser with the 180gr Ballistic Tip. Here's the load data for the 8mm JS Mauser with the 180gr Ballistic Tip:
Starting: 43.0grs IMR 4064 (most accurate load)
Max : 47.0grs IMR 4064
As always start low (in this case you may want to stay low), and work your way up carefully.
